﻿Carexduanensis (Carexsect.Rhomboidales), a new species of Cyperaceae from limestone areas of Guangxi, China

﻿Abstract Carexduanensis Z.C.Lu, Y.F.Lu & X.F.Jin, a new species in limestone areas of Guangxi, China, was discovered and described. The morphology showed that C.duanensis is similar to C.calcicola, but differs in having culms central, leaf blades 3–5.5 mm wide, bracts longer than spikes, utricles 4–5 mm long, shorter, and nutlets abruptly contracted into an erect beak at apex. SEM microphotographs of utricles and nutlets are provided for the new and related species, C.calcicola.


Introduction
Cyperaceae (sedges), containing 5600+ species in 95 genera worldwide, are the third largest monocot family.It is distributed from tropical to Polar regions, from alpine meadows to tropical rainforests, from Gobi deserts to swampy wetlands, and plays a crucial role in various ecosystems (Larridon et al. 2021).The genus Carex L., comprising ca.2000 species, stands as the largest genus within Cyperaceae and is distributed almost worldwide (Reznicek 1990;Starr and Ford 2009;Roalson et al. 2021).Recent phylogenetic studies have provided a framework for identifying morphologically diagnosable lineages within Carex, organizing it into six subgenera: Carex subg.Siderosticta, C. subg.Psyllophorae, C. subg.Euthyceras, C. subg.Uncinia, C. subg.Vignea, and C. subg.Carex.Moreover, the genus was subdivided into 62 formally named Linnean sections plus 49 informal groups (Roalson et al. 2021).Carex is one of the largest genera of angiosperms in China, boasting representation of more than 700 species (Chen and Zhang 2018).
During the investigation from May 2021 to March 2023, we collected specimens of Carex with mature nutlets from limestone evergreen broad-leaved forests and shrubs in Du'an County and Yizhou City, Guangxi, China.After carefully checking the morphological characters of these specimens and comprehensively consulting relevant literature, with comparison of nutlet and utricle micromorphology (Dai et al. 2000(Dai et al. , 2010;;Jin and Zheng 2013;Jin et al. 2014;Chen and Jin 2015;Yang et al. 2015aYang et al. , 2015bYang et al. , 2016;;Roalson et al. 2021), we confirmed it as a new species of C. sect.Rhomboidales and described below.

Materials and methods
Specimens of this new species were collected from Du'an County and Yizhou City, Guangxi, China.After that, we carefully studied relevant literature and the morphological characters of the specimens, which involved measuring and recording the size, shape, and color of rhizomes, culms, leaves, bracts, spikes, glumes, utricles, and nutlets.We examined herbarium specimens at BM, E, HTC, IBK, IBSC, K, KUN, P, PE and ZJFC.The other related species of Carex sect.Rhomboidales were examined online images from Kew Herbarium Catalogue (http:// apps.kew.org/herbcat/gotoHomePage.do), JSTOR Global Plants (https:// plants.jstor.org/)and Chinese Virtual Herbarium (https://www.cvh.ac.cn/).SEM (scanning electron microscope) observations of utricles and nutlets of the new species and the similar species Carex calcicola Tang & F.T.Wang in C. sect.Rhomboidales were carried out.Mature utricles and nutlets were gathered from specimens we collected, the specimens 'W.B. Xu, C. R. Lin & Z. C. Lu 14641' for the new species and 'X.F. Jin & al. 2391' for C. calcicola respectively.The utricles were submerged in 50% ethanol to clean for 2 hours, then air dried.The cleaned utricles were mounted on stubs by doubled-sided adhesive tape and coated with gold.The nutlets were initially soaked in a solution of concentrated sulfuric acid and acetic anhydride (volume ratio = 1:9) for 16 hours, then rinsed in acetic acid for 10 min and water for 5 min, and placed in a bath-type ultrasonic cleaner for 30 min with 70% ethanol to remove the cuticle and outer periclinal wall of the epidermis (Jin et al. 2014).After air drying, the nutlets were also mounted on stubs using double-sided adhesive tape, and directly coated with a layer of gold.The coated utricles and nutlets were observed and photographed under a GEMINI-300 scanning electron microscope (SEM).Diagnostic description.This new species is similar to Carex calcicola Tang & F.T.Wang, but differs in having culms central (vs.culms lateral), leaf blades 3-5.5 mm wide (vs.7-15 mm wide), bracts longer than spikes (vs.shorter than spikes or nearly equal in length), utricles 4-5 mm long (vs.5.5-6.5 mm long), shorter, and nutlets abruptly contracted into an erect beak at apex (vs.curved or coiled beak at apex).
Etymology.The specific epithet 'duanensis' refers to the type locality of this new species.
Phenology.Notes.Carex duanensis has nutlets rhombic-ovoid, obtusely trigonous, with 3 angles constricted at middle, sides concave above and below, apex abruptly contracted into a ca. 1 mm long beak, beak erect or slightly curved, annulate at orifice.Based on these morphological characters, C. duanensis belongs to C. sect.Rhomboidales and is similar to C. calcicola (Dai et al. 2010), but differs from the latter in having culms central, leaf blades 3-5.5 mm wide, bracts longer than spikes, utricles 4-5 mm long, shorter, and nutlets abruptly contracted into an erect beak at apex.The morphological differences of C. duanensis and C. calcicola are shown in Table 1.

Figure 1 .
Figure 1.Carex duanensis sp.nov.A habit B lateral spikes C utricles D nutlets E pistillate glumes of middle and upper part F staminate glumes.

Figure 2 .
Figure 2. Carex duanensis sp.nov.A habit B staminate glume C pistillate glume of basal part D, E pistillate glumes of middle and upper part F utricle G nutlet.(Drawn by Xiao-Feng Jin; based on the holotype: W.B.Xu et al. 14641 in IBK).